Power of Love
by me and Mr. Jones
Summary: Alec is possessed by his son Max's biological demon father who tries to make Max chose between blood and family. For Max it's an easy choice but is the answer worth the risk to Alec's life? Read and find out! No character death. First Mortal Instrument Fic.


_I don't own anyone or anything in this story. This is my first Mortal Instrument fic so… please be kind._

Max stared at his father, his blue eyes were now black, a sign of the demon possessing him.

"Dad," the warlock whispered before looking over at his Papa and brother lay unconscious after the fight. They were alive, Max could see their chest rising and falling but now it was just him and demon. The problem was Max couldn't use magic and run the risk of hurting his dad, something he was sure the demon was counting on.

Suddenly Alec's blue eyes replaced the black.

"Max, Run!" But then the eyes were black again.

"Leave and I kill all three of them," the demon threatened. The 12 year old nodded, he wasn't going anywhere if it meant risking his family.

"What do you want?" He tried to sound tougher than he felt. Rafe was the brave fighter, Max was a pacifist and wasn't one to use magic often. The demon laughed and Max flinched, his dad's laugh should never sound that hateful.

"For you, my son, to see your full potential." Max had known the demon was his biological father immediately, almost as if he'd seen him before. Alec and Magnus had known too. However, he felt nothing more than distain for this monster that had attacked them unprompted.

"I am not your son," Max growled. The demon blinked slowly, it appeared that the demon was almost distracted by something else happening, and Max wondered if Alec was putting up that much of a fight.

"My blood runs through your veins, blue one, and I can smell the power within you, whether you admit it or- silly shadowhunter you are not strong enough- whether you admit it or not."

"Blood doesn't equal family, love does and I have no feeling for you other than hatred," Max claimed. "Dad, keep fighting, don't give up." He pleaded, Max would always go to Magnus for warlock things, but when it came to just feeling like a kid, Alec was his go to parent. The demon hissed and when he opened his eyes again they were blue.

"Maxie, I need you to call him out," Alec told him, his voice shaking under the strain of holding back the demon.

"No! I could kill you and even if not, I'm not strong enough," Max said desperately, hoping that his father had another plan, but he could see Alec was losing the fight of control.

"You are strong enough, you are my-" Black eyes glared and a scowl fell on Alec's lips.

"Filthy Nephilim, the longer you fight, the faster you die," he snarled. Max's stomach dropped, "But you are right, you are not strong enough to call me out, but you could be, one day, with my training." He said to Max and Max wanted to stab him with a seraph blade, but that would kill Alec too.

"You think I'm just going to leave with you, train under you to become an evil piece of shit like you?" Having never been hit straight on before when it wasn't in training, the backhanded slap that the demon delivered took Max by surprise. He wondered if the strength behind the hit was the demon or Alec's body. He knew he was strong, but his father had never so much as grabbed him with any amount of force so he couldn't be sure.

"Do not speak to me that way, I am your father," the demon said with calm anger.

"You are not my father!" Max cried. "My fathers are Alexander and Magnus Lightwood-Bane. I am half demon, but because of them I follow my human side" Max could feel his magic bubbling to the surface, ready to be used. "Every day I have the choice to use my magic for evil, or I can choose to be the person my fathers raised me to be, the kind, strong, _soul_ they see me as. You have no chance here. I will never go with you, this is my family, this is where my power comes from, not you!"

There was a moment of pause before a knife appeared in the demon's hand and held at Alec's throat.

"NO!" Max yelled. His magic faded and he just felt like a terrified kid.

"Shame, you gave in so easily. Ah well, that can be changed," the demon lowered the knife and shook his head. "Lightwood is a fighter, I'll give him that, but he's not going to last much longer." Max inhaled a shaky breath at the thought of losing his father. A small groan pulled his attention away from the demon, Rafe started to wake up but Max used magic to put him back asleep, not wanting his hot headed brother to get hurt.

"Smart boy," the demon said. Then his eyes were blue again,

"You have to use your magic on me, it's the only way, I don't have much left in me. Please Max, Papa and Rafe need you more than they need me," Alec begged the impossible of his child. Max could see him fading, he could see the exhaustion and pain in his eyes. "You are stronger than you know, and I am so proud of you, I love you," Alec gave up, Max could see it even before the eyes turned black again.

"No! Daddy no!" Max grabbed Alec's shirt, begging him back but the demon threw him off, Max collapsed on the floor, crying as the demon stood over him.

"He's quiet now," the demon said smugly.

"Noooo," Max sobbed, "Why do you want me? Surely you have other children, better children." The demon shrugged,

"Probably, but I couldn't pass on the chance to take down a shadowhunter."

Those word caused Max's head to snap up, the magic was back. He sent a wave of anger, causing Alec's body to stumble back.

"Not bad kiddo," the demon chuckled. Tears blurred the details of his possessed parent, or was it just his body now? Max wasn't sure. Suddenly Max was thrown back against the wall. "Don't be sad, sadness is useless to us, anger is what makes us powerful."

 _Emotions are distractions._ It was something the clave still tried to teach but something Alec did not believe and refused to let Rafe and Max believe it either. 'Love is not a distraction, it's something to bring focus. Love makes everything clear, use it and you become unstoppable.' Alec word played in his head. Max turned to his unmoving family, he couldn't lose them too. He could fight the demon and possibly lose his dad or he could give in to the demon and lose them all.

Max stood up, bracing his stance, fully focusing on his family and his love for them. The love they gave him so willingly and unconditionally when the woman who gave birth to him could not find it to give. The love they taught him to give to himself, especially when that felt impossible. The love they showed him when loving himself _was_ impossible. The love he had for his brother who said Max was his parabatai regardless of the stupid clave rules. The love he had for his Papa whose magic was used to show the goodness in the demon blood that so many feared or hated. The love for his dad who taught him that family was what you made it and blood and downworlder status had no power in stopping family.

His entire body was bursting in magic. He opened his eyes and directed that magic at Alec, trying to aim for the demon inside him and not Alec's soul. The blast pushed the demon out and destroyed half the apartment. The demon screamed as he was banished and Alec and Max collapsed to the ground. The force of the magic taking nearly everything out of him.

"Dad," Max whimpered, crawling to the limp body, praying to the angel that he had not just killed Alec.

"My little blueberry," came the quiet voice before the blue eyes opened. Max groaned in relief as he laid his head on Alec's chest.

"I thought I'd killed you," Max whispered weakly. There was silence with only the sound of Alec's shallow, feeble breaths and Max looked at Alec's face and wondered if he had indeed failed to save him.

"I knew you could do it," Alex claimed, brushing Max's hair out of his face. Max could tell Alec was dying.

"Dad, please, don't, I don't have the strength to save you," Max pleaded.

"Shhhh," Alec smiled sadly. "You were incredible, baby, you don't need to worry about me anymore." His eyes were closing and Max knew they wouldn't reopen, blue or otherwise if he didn't do something. He put his hand on Alec's barely moving chest and used whatever he had left to shoot healing magic in him, he passed out not knowing if it had made a difference.

Max could feel himself coming to, he was so tired, he'd never been so tired, still, heal, he had to heal. He felt the warmth in his fingers, hoping his hand was where it needed to be to save Alec.

"Dad-Daddy wake up," he muttered.

"Blueberry, no, no," Magnus's voice gentle but clearly distressed. "No more magic," one hand was in his hand and other was on his face.

"But Dad-" Max whined, trying to make his eyes open to figure out what was happening.

"You already saved him," Magnus reported. "You need some sleep; Dad will be here when you wake up." Finally Max's eyes obeyed and opened slightly, just enough to see Magnus's tear stained face.

"I did it?" Max asked, "I healed him?" Magnus smiled wetly at him.

"Yeah baby, you did it," the cat eyed warlock kissed his son's forehead. Max began to cry,

"I did it!" he said happily, "I didn't think I could but I did…" tears were streaming down his face as he passed out in exhaustion again.

The next time he woke up he actually felt like he'd slept and as he opened his eyes the first sight he saw was his dad's face inches from his. It appeared Alec had fallen asleep in his bed, his arm draped over Max as if protecting him. Then Max felt warmth and weight curled around his back and based on the size, he knew it had to be Rafe. Then Max realized there was yet another arm coming from behind and recognized it as Magnus's arms. He figured out they were all in Magnus and Alec's bed cocooning each other. Max grinned, this was what the demon would never be able to understand. The greatest power didn't come from who you were born from, it came from who you loved and who loved you. And that made the Lightwood-Banes the most powerful family Max could imagine.


End file.
